1. Field of the Invention
The present invention relates to a drive signal generation circuit for driving loads such as light-emitting devices, including semiconductor devices and electron-emitting devices, according to gradation data, and to an image display apparatus using the drive signal generation circuit. More particularly, the present invention relates to a drive signal generation circuit suitable for simultaneously driving a plurality of loads such as light-emitting devices connected to wiring having inductance and capacitance components, and to an image display apparatus using the drive signal generation circuit.
2. Description of the Related Art
Heretofore, image display apparatus having an image display panel in which a plurality of light-emitting devices such as electron-emitting devices, light-emitting diodes (LED) or organic electroluminescent (EL) elements are connected by matrix wiring are known. Image display apparatus using such light-emitting devices are advantageous in that they require no backlight since they are of a self-light-emitting type, and that they have a wide viewing angle.
As methods of driving light-emitting devices connected by matrix wiring, methods using pulse width modulation (PWM), pulse-amplitude modulation (PAM), and a combination of pulse width modulation and pulse-amplitude modulation are known. Various circuits' arrangements for performing these kinds of modulation have also been provided.
With the increase in the number of gradations in displays using conventional drive methods using pulse width modulation or pulse-amplitude modulation, a need for operation at a higher speed has arisen with respect to the pulse width corresponding to the least significant bit (LSB), i.e., the minimum unit of data, or for higher output accuracy with respect to amplitude values. Therefore methods using a combination of pulse width modulation and pulse-amplitude modulation have come into use.
Matrix wiring connecting devices has, however, inductance components and capacitance components. If gradation control of devices connected to such wiring having inductance components and capacitance components is performed by a combination of pulse width modulation and pulse-amplitude modulation, ringing occurs in each of rises and falls of the signal waveform to cause a difference from the desired waveform according to data.
In a case where devices arranged in parallel with each other, for example, in correspondence with information signal electrodes in matrix wiring in an image display panel are driven by a plurality of drive signal generation circuits, if a certain number of the devices are driven simultaneously, the current flowing from each drive signal generation circuit to the devices is increased, and influences which a drop in the voltage of the output power supply and a voltage drop across a wiring resistance due to the difference in current value give to the signal for driving each device largely vary.